Treatment of primary tar acid compounds



May 22, 1962 K. M. BLEESE TREATMENT OF PRIMARY TAR ACID COMPOUNDS Filed March 20, 1957 LlghT Fracflonaror Tar Tower I NoOH SOIV.

r 10 i V NeuTra\O|ls Crude Tar sflllbr g g jgg coal FracTionaTor ep y 4 Heavy Tar Olls For Vessel Forming creoso'Te cres We W UnsaTuraTed Hydrocarbons I41 y I OlherH drocarbons Ana wa r Punher or SUN u g. W er cres me Purified 6rids i \I: J5 Refined Tar Acid FracTiOfls I J7 -CO3 Carbonalor Pnmary Tar Aclds Tower FracTionaTor Tower Sod1um Garbonafe OenTrifuge fieparafory Vessel INVENTOR.

Ker/nil M. fi/eese BY Stats My invention and discovery relate to a purification treatment of primary tar acid compounds.

More particularly, my invention and discovery relate to the removing of neutral oils, unsaturated hydrocarbon compounds and other foreign hydrocarbon compounds from tar compounds resulting from carbonization or distillation processes other than high temperature carbonization or distillation of bituminous coal, sub-bituminous coal, lignite coal, shale and the like. Such processes other than high temperature carbonization or distillation of bituminous coal, etc. are hereinafter referred to as low temperature carbonization or distillation of such bituminous coal, sub-bituminous coal, lignite coal, shale and the like.

Briefly stated and more particularly, my invention and discovery relate to the process of removing the neutral oils and unsaturated hydrocarbon compounds and other foreign hydrocarbon compounds from crude primary tar acid compounds as received from the tar stills, i.e. after such primary tar acid compounds are separated from the tar oil creosote. The impurities or contaminating portion constitute but a small part of the materials as a Whole received from the tar still.

The object of my invention and discovery is to remove the relatively small amount of impurities or contaminating elements which are present with the primary tar acid compounds as they come from the tar still, i.e., my object is to remove the relatively small amount of such impurities and contaminating elements from the larger mass thereof in contrast to the accepted procedure attempted heretofore which follows the idea of removing the large mass of primary tar acid compounds from the relatively small amount of impurities or contaminating elements. Such attempts have not proven successful. Accordingly, my invention operates to develop a condition in the crude primary tar acid materials which permit the breaking down of the bond between the unsaturated compounds and the other undesirable hydrocarbon compounds from the primary tar acid compounds. This procedure or approach permits the carrying over of the freed impurities with the distilling water.

The purified primary tar acid compounds are then ready to be fractionally distilled to yield valuable products, namely, phenol, o-cresol, m and p-cresol and xylenol oils. The portion remaining after distilling the above fractions may be used too as a wood preservative or may be used to fortify the tar acid content of wood preservative creosote. Also such portions remaining after distilling the above named fractions may be subjected to the formaldehyde condensation process for the formation of synthetic resin for shingle staining and various other types of wood coatings.

When primary tar acids are formed or derived from the low temperature carbonization process, foreign and unsaturated hydrocarbon compounds remain attached to the primary tar acid compounds. This is in definite contrast to those primary tar acid compounds derived from high temperature carbonization where the temperature is sufli ciently elevated during carbonization to remove these foreign and unsaturated compounds by cracking and then distilling them. In the low temperature carbonization process on the other hand, the unsaturated compounds appear to act as isomers attached to the primary tar acid compounds and so resist separation and distillation from the tar acids. Thus, unsaturated compounds so remain attent vous light oils and coal tar oil fractions.

tached to the primary tar acids despite successive distillation, even after an extended number of redistillations in an effort to purify the primary tar acids. This explanation for the failure to bring about a separation was discovered by me only after a great many unsuccessful experiments. Such difference in distillation reflects the great difference in age of the two coals.

The failure to bring about such separation or purification in the low temperature process is revealed by the fact that such primary tar acids with the unsaturated compounds as heretofore attained turn dark after the lapse of a short period of time because such unsaturated compounds absorb oxygen from the air and thus clearly disclose their non-separation. This discoloration greatly reduces the commercial value of such unpurified tar acids. Furthermore, another serious objection to such tar acids as are attempted to be obtained by the low temperature carbonization process is that they do not produce a commercial grade synthetic phenolic resin unless the tar acids are first fortified with tar acids from high temperature coke oven tars. Even with such fortification, the resulting resin is of inferior grade being of dark color and an objectional odor. Because of these characteristics, such low temperature carbonization tar acids have not found a ready commercial market. Such fortifying process has not constituted an economical procedure for utilizing these primary tar acids. Their noted defects above have proven too serious. It may be asked if there are so many defects to the low temperature carbonization process then why not employ only the high temperature carbonization of hydrocarbons exclusively. There are several reasons which amply answer this question. If the problem of separation of the impurities or contaminating elements from the true primary tar acid compounds can be successfully and economically accomplished, then an almost unlimited source for raw materials is provided from which very valuable by-products may be obtained. This source of primary tar acids is much greater for low temperature distillation processes than 'for the high temperature distillation processes. The second reason is, that with the low temperature distillation process there is recovered a much greater proportion of condensable volatiles than gases (gas being a non'consensable volatile). Furthermore, another reason for exerting every effort to solve the problem of purifying crude primary tar acids derived by low temperature carbonization resides in the fact that there are many types of coals such as sub-bituminous and lignitic or noncoking coals that do not well lend themselves to high temperature treatment.

In the pyrolises of coal there are obtained the following products: (A) Non-condensable gases, (B) condensable volatile products, and (C) solids. The solids are ob.- tained in the form of coke or char. The condensable volatiles constitute the light oil and coal tar. The light oils and coal tars are separated from the gases by condensation from the gases. The condensation step, which is a part of the carbonization process, involves passing the hot volatile bearing gases coming from the carbonizer through the gas scrubbers, i.e. often through water sprays. The condensation products comprising light oils and coal tars are separated from the water and subjected to distillation by conventional distillation methods resulting in the vari- The crude primary tar acid compounds are present in the various coal tar oil fractions. These coal tar oil fractions are then subjected to hydroxide treatment whereby the crude tar acids are dissolved out, forming a phenolate or a product commonly known as cresylate or carbolate.

The method of treatment of my invention and discovery is as follows:

The crude primary tar acid compounds constitute an abundant source of primary tar acid compounds which it swans ured.

is the object of my invention and discovery to provide in their purified state. These primary tar acids in their purified state, in turn, serve as the source of many valuable by-products. However, as these primary tar acid compounds are obtained and received in their crude state from the tar stills the primary tar acid compounds are intermixed with (1) neutral oils, (2) unsaturated hydrocarbon compounds, and (3) other foreign compounds. This intermixture of crude tar acids comprises the raw materials for my treatment, i.e. to be brief, the same are herein referred to as the crude tar acid intermixture. The first step of the process of my invention and discovery consists in adding to said crude tar acid intermixture a hydroxide, (sodium or potassium) solution to form the 7 basis for the separation of the neutral oils from the primary tar acid compounds and their contaminating hydrocarbon compounds. This hydroxide treatment is done by way of a preliminary test of theparticular supply of crude tar acid intermixture to determine the percentage of primary tar acids present. V

' This hydroxide test treatment comprises the following: 100 cc. of what is termed above the crude tar acid intermixture is measured in a vessel. Next a 25% solution is formed of sodium hydroxide using 100 grams of sodium hydroxide and 300 cc. of water. This amount of sodium hydroxide is intentionally in excess of the true amount required for eflicient operation. The 100 grams of sodium hydroxide and the 300 cc. of water constitute a 300 cc. sodium hydroxide solution. The 300 cc. solution is then mixed with the 100 cc. of the crude tar acid intermixture and allowed to stand in a settler or separatory funnel. That portion of the crude tar acid intermixture consisting of the primary tar acid compounds and the unsaturated hydrocarbon compounds and foreign compounds settles to the bottom leaving the neutral oils to rise. to the top as a layer. The settling portion is sometimes called cresylate or phenolate or carbolate. The cresylate is then separated by drawing it 01f from beneath the neutral oils in a separating funnel. A 20% solution vof sulfuric acid is then added to the cresylate until the sodium hydroxide is all neutralized and slightly acid to the point Where it turns blue litmus pink and all of the primary, tar acid compounds and the unsaturated hydrocarbon compounds are freed, the primary tar acid compounds rising to the surface in a layer on the neutralized sodium hydroxide solution. The neutralized sodium hydroxide solution is drawn off from the bottom of the separatory funnel leaving the primary tar acid compounds. The tar acids rise to the sur face of the neutralized sodium hydroxide solution in 'a layer. The crude tar acids are recovered from thesettler funnel by first draining 01f the neutralized sodium hydroxide solution (sodium sulphate) and then are drained 01f the-crude primary tar acidhydrocarbons which also include' the unsaturated hydrocarbons and the foreign compounds, i.e. all of the intermixtures minus the neutral oils. The volume of the crude primary tar acids is then meas- Thus, the percent of crude primary tar acid hydrocarbons, unsaturated hydrocarbons and foreign compounds, present, in the original intermixture of the material as received from thetar stills, can be determined.

That is, the amount of the primary tar acids present in the 100 cc. crude tar acid intermixture is divided by the 100 cc. of the crude tar acid intermixture. The percent may amount to 25 to S percent.ordinarily about 35 percent. Thus, the amount of sodium hydroxide required to treat a given amount of crude tar. acid intermixture is determined. From chemical texts, it is known that one gram sodium hydroxide is required to dissolve three grams of primary tar acids. 7 e Havingdetermined the percentage of tar acids in the crude far acid intermixture, it is now possible to treat the crude tar acid intermixture with an efficient amount of hydroxide solution. V

Accordingly, my invention and discovery comprises the following procedure: r

On the basis of the cc. crude tar intermixture test above set forth, it was determined that the amount of primary tar acid present in the crude tar intermixture was from 25% to 50% and from chemical texts it is known that one gram of sodium hydroxide will dissolve three grams of primary tar acids. Assume that the test set forth above shows that the particular sample of crude tar acid intermixture gives a primary tar acid content of 35%. Thus, for example, 100 lbs. of crude tar acid intermixture contains, on the basis of the test, 35% of primary tar acids, i.e. 35 lbs. This I wash with a hydroxide solution containing 11.6 lbs. of sodium hydroxide which is dissolved in 104.4 lbs. of water-which means a 10% solution concentration and total weight of 116.0 lbs of solution. There the 100 lbs. of crude tar intermixture is treated with the 1 16 lbs. of 10% sodium hydroxide solution. This treatment dissolves the primary tar acids and thus separates the neutral oils (aliphate or straight benzine) from the phenolates or cresylates. The mixture, upon standing, separates by gravity, the neutral oils rising to the top as in the test and the phenolates or cresylates settling to the bottom. The mixture then may be separated in various ways, as by drawing olf the cresylates from the separatory vessel from beneath the neutral oil layer. Centrifuging may be employed or other separating means.

The phenolate or cresylate is then heated in a closed vessel equipped with a straight condenser. As the heating proceeds, the dehydration of the hydroxide solution takes place and the water distills over. The freed impurities in the form of unsaturated and other foreign hydrocarbon compounds pass over with the distilling water. Note well that this is not steam distillation but rather in my process dehydration of the original sodium hydroxide solution. In true steam distilling, steam or even water is added during the process of distillation. In contrast, in my process I add no water or steam and in fact, my purifying process involves no hydrocarbon distillation. My process operates to dehydrateor drive off the water present in the sodium hydroxide solution by reason of the gradual temperature elevation thereby concentrating the remaining sodium hydroxide solution. This operates, I have discovered, to produce a closer bond between the sodium hydroxide and the primary tar acid compounds which resist any distilling over. This results in my process of lessening or breaking the bond between the unsaturated hydrocarbon compounds and other hydrocarbons with respect to the primary tar acid compounds because of the temperature elevation and increase of hydroxide concentration. In my process, the Water being distilled operates as a mechanical vehicle to carry over the said freed and undistilled unsaturated compounds and the other contarninating hydrocarbons. The sodium hydroxide becomes more concentrated as the temperature increases to or approaches the temperature of the order of to 160 C. Ordinarily C. is the approximate temperature.

, This treatment is continued until the water distillate becomes clear and nofurther contaminating compounds are carried over are present. With some few contaminating hydrocarbons this may extend a little beyond the 0.: Taking the primary tar acid compounds as a whole the temperature for treating the cresylate which at the point after heating comprises the primary tar acids dissolved in the hydroxide solution, ordinarily need not reach 160 C., but certain isolated tar acid fractions require evenhigher temperaturesof the cresylate to purify the primary tar acids. This applies to certain high boiling primary tar acids which normally are beyond the range in which commercial primary tar acids are found.

The next step is to dilute back the phenolate or cresyl- 'ate with the addition of water to a preferred concentration of 20% or any desired working concentration. This is necessary to prevent the cresylate from solidifying upon cooling to room temperature.

Finally the phenolate or cresyiate is sprung, i.e.

neutralized by adding a mineral acid or carbon dioxide gas. Ordinarily, when an acid is used, sulphuric acid is selected. Phosphoric acid may be substituted as the acid and this provides for the production of sodium phosphate which may be further processed and form a fertilizer or other products, as for example, leather dressings or wetting agents. In common practice, carbon dioxide gas is generally employed.

Accordingly, my method of tar acid purification makes use of both the elevated temperature of the phenolate or cresylate and the simultaneously increased concentration of the sodium hydroxide, both being necessary to pro ceed together. This procedure provides, as it were, two forces: On the one hand, a separating force for the impurities portion which causes them to separate or be freed and thus be mechanically carried over with the distilling water; and on the other hand a binding or holding force which locks the primary tar acid portion to the hydroxide portion of the cresylate, and thus the primary tar acid portion or multi-fractions are prevented from separating or passing over with the distilling water.

A sample of crude primary tar acids as received from the gas scrubbers, which crude primary tar acids are derived from the lignite carbonization process, was tested for comparison purposes as follows in the making of synthetic phenolic resins: In one experiment the crude primary tar acids were extracted and treated by the conventional methods employed in extracting primary tar acids from high temperature coke oven tars. That is such method is the usual method for treating high tem perature tars but as the tests show is not adaptable to low temperature produced tar acids, which establishes the absence, previous to that herein set forth, of a com merical successful purifying process for said low temperature tar acids; and in the other the technique of my invention and discovery above set forth was adopted. The results obtained were as follows:

Regular Method for High Temperature Produced Tar Acids Phenol distilled over with water, dark color Bakelite resins:

A stage: Not complete after 80 minutes C stage: Crumbly resins, did not adhere to metal Odor of resin: Amine like Invention of Applicant Designed Especially for Low T emperature Produced Tar Acids Phenol distilled over with water, clear colorless Bakelite resins:

A stage: Complete by 66 minutes C stage: Hard resin, adhered to metal Odor of resin: Clean, clear phenolic A total of impurities, i.e. unsaturated and other contaminating hydrocarbons, in the amount of about 5% is provided by the following of the process of my invention and discovery.

The above results show that a definite improvement in handling these low temperature produced tar acids is effected by the treatment of the applicant.

In the above I have disclosed my invention and discovery employing the batch method. In the following, a continuous processing method is set forth for my invention and discovery.

Crude coal tar received from and formed by the apparatus called a carbonizer is conducted to the device called tar still or fractioner where the primary tar acid intermixture (i.e. coal tar distillate as known in the industry) is distilled. Such primary tar acid intermixture or coal tar distillate enters the bottom of the fractionator tower or column 11. As the vapors rise through the multi-plates of the tower, the desired coal tar distillate fractions are separated from the intermixture mass. The desired fraction or group of primary tar acids are separated at a temperature 175 C.-245 C. and pass to the mixer 12. The remaining fractions with the higher boiling points are drained off at a lower level of the fractionator tower and used as a preservative, known as creosote.

To the removed fraction of coal tar distillate or group of primary tar acids intermixture is added the 10% solution of sodium hydroxide of the required proportion (determined as fully set forth in the above disclosure of the batch treatment). The sodium hydroxide solution dissolves the primary tar acids and frees the neutral oils (called neutral because they are not affected by alkalies). The contents of the mixer 12 pass to the separatory vessel or centrifuge 13 where the neutral oils are removed. (In the separatory vessel, the neutral oils rise to the top as above described in the batch system.) The primary tar acids are passed to the purifier or distilling vessel 14 where the dehydration of the cresylate takes place. Here, the temperature is raised to .C. C. In the vessel or still the simultaneous action of elevating the temperature and increase in concentration proceeds. The result is the freeing of the unsaturated and other contaminating hydrocarbons while the bond is increased which binds the true primary tar acids to the sodium hydroxide while breaking the bond of the unsaturated and other contaminating hydrocarbons for the primary tar acid hydrocarbons.

The purified cresylate from vessel 14 is passed to the neutralizing or carbonator tower 15 equipped with grids. Water is added to the cresylate preferably being introduced just prior to the entry of the cresylate into the neutralizing tower 15, to stabilize the cresylate. At the bottom of tower 15, carbon dioxide is introduced for the purpose of neutralizing the cresylate to a pH of 6.2 and freeing the tar acids from the sodium hydroxide by forming sodium carbonate.

Next, the mixture of neutralized sodium hydroxide and freed tar acid are introduced into a centrifuge or separating vessel 16. The sodium carbonate is removed and the purified primary tar acids are passed to the tar acid fractionator. The temperatures in this tower vary and at the following (i.e. substantially) temperatures various frac tions are removed. Five hundred cc. sample of given primary tar acids which have been subjected to the purifying treatment embodying my invention and discovery yield fractions distilled as follows:

ing the crude tar acids derived thereby according to the process embodying my invention and discovery the total value of a ton of carbonized coal yields the following:

Total value of a ton of carbonized sub-bituminous coal, employing my process to refine the acids.

Char recovered, 12,000 Btu., d7.5% 950 lbs. $10.00 per ton Coal tar recovered, 232 lbs, 60%, coal tar pitch or 139 lbs. $41.20 per ton Coal tar oils 93 lbs. or 11.6 gals.

34% of lbs. coal tar oil intermixture is not usable for commercially tar acids extraction, but good only for wood preservatives or 31.6 lbs.

66% of 93 lbs. coal tar oil intermixture is usable for commercially tar acid extraction. 66% of '93 lbs. usable intermixture.

40% of 61.4 lbs. intermixture or 24.5 lbs. crude tar acids.

60%1 of 61.4 lbs. intermixture or 36.9 lbs. neutral or s.

Pyridine base oils present "3% boiling range 160 C.250 C. 3% of 36.9 1bs.:1.1 lbs. pyridine oils $2.77

per c.

1.8 lbs. per gal. or pyridine oils per ton of neutral oils,

. .38 36.9 lbs neutral oils less 1. 1 lbs. pyridine or 35.8

Ortho cresol 10% of 24.5 lbs. or 2.4 lbs.

17 per lb. Ortho cresol per ton coal $.04

. Meta para cresol 25.7% of 24.5 lbs. or 6.3

lbs. 13 per lb. Meta para cresol per ton coal Xylenol oils 27.3% of 24.5 lbs. or 6.7 lbs.

@ 20 per lb. ylenol oils per ton coal 1.34

V Total value of refined tar acids per ton sub-bituminous coal 34% of 93 lbs. coal tar oil intermixture, not usable for commercial tar acid extraction, but suitable for wood preservahive creosote. Per ton bituminous coal,

coal, lhs 1.5

Jlotal wood preservative creosote or 8.3 gal. 22 per gaL, lhs 68.9

Total value per ton carbonized sub bituminous coal when using my tar acid refining process $13.36

An alternate procedure for the batch process is the following continuous extraction and purification process:

First mix up 40% solution (instead of 10% solution as in first procedure) of water and sodium hydroxide and heat to 140 C. temperature, then mix the proper amount of sodium hydroxide solution and tar oil intermixture fraction 175 C.24S C., or higher boiling range intermixture fraction tar oils if desired, in a heated separatory vessel and leaving the mixture to separate by settling. The neutral oils will rise to the surface of the liquid and the cresylate will settle to the bottom; or the cresylate may be separated from the neutral oils by means of a centrifuge.

Second, the hot cresylate is then introduced into either batch cresylate purifier or continuous purifier 14, the temperature of the cresylate is then raised slightly, to about 145 C. and a small continuous stream of water introduced into the purifier, the temperature of the cresylate being maintained at 145 C., more or less as found to advantage. Thus, the water introduced into the hot cresylate in the purifier vaporizes and the water vapors assist in mechanically carrying over the, freed unsaturated and other contaminating hydrocarbons, by carrying them along into a condenser (not shown) where the water vapor is entering the liquid phase. The water vapor being mixed with the unsaturated and other contaminating hydrocarbons is run through a gravity oil, separator, the water having the higher specific gravity and the rate of flow of oils noted, to determine if all of the unsaturated and contaminating hydrocarbons are being removed from the cresylate. Also, these unsaturated and contaminating hydrocarbons are thus recovered for possible use, or mixed with the creosote.

The amount of unsaturated and other contaminating hydrocarbon oils present in the cresylate is determined by running a laboratory size sample of the unrefined cresylate through the purification process in the laboratory, to establish the definite proportion between the'volume of I water vapor condensing and. the volume of unsaturated and other contaminating hydrocarbon oils to be removed from the unrefined cresylate. This supplies the basis for determining the volume of water to be added to the hot cresylate of 40% hydroxide content to provide the vehicle for mechanically carrying over the freed unsaturated I prefer the first procedure set forth rather than the alternate procedure because by the alternate procedure I do not get as refined a product as by the first procedure. There is a tendency for the neutral oils to become saponified or emulsified. Such saponification or emulsification may be avoided or minimized by keeping the addition of sodium hydroxide or alkali at the exact proportion or slightly less than is required to fully dissolve all of the tar acid.

I claim:

l. The process of producing primary tar acids from crude coal tar and shale oils obtained by low temperature distillation of a member selected from the group consisting of oil shale, bituminous coal, sub-bituminous coal, l-ignite coal, and mixtures thereof, said shale oils and said crude coal tars comprising light tar oil fraction and heavy tar oil, coal tar pitch and creosote, said light tar oil fraction comprising the intermixture of primary'tar acids, neutral oils and unsaturated and other contaminating hydrocarbons from which intermixture the primary tar acids are to be separated, said process comprising the following steps in sequence: separating the light tar oil fraction; reacting the light tar oil fraction with an alkali metal hydroxide in aqueous solution the concentration of which is effective to form a solution of cresylate in aqueous alkali metal hydroxide and freeing substantially the neutral oil part of said fraction; separating said neutral oil part by virtue of its specific gravity from the solution of cresylate in aqueous alkali metal hydroxide which solution of cresylate in aqueous alkali metal hydroxide then comprises the primary tar acids, unsaturated and other contaminating hydrocarbons; and separating said primary tar acids from the unsaturated and other contaminating hydrocarbons by simultaneously subjecting said solution of cresyl-ate in aqueous alkali metal hydroxide to progressively increasing elevated temperatures and increased alkali metal hydroxide concentration caused by dehydration vapors formed by heat of a temperature magnitude of the order of C.l60 C. at atmospheric pressure, said vapors carrying 05 the freed unsaturated and other contaminating hydrocarbons leaving the primary tar acids undistilled a purified cresylate.

2. The process of claim 1, wherein the concentration of the solution of aqueous alkali met-a1 hydroxide, with which the light tar oil is reacted, is 10%.

3. The process of claim 1, 'and further, adding water to said purified cresylate, which water prevents the cresylate from solidifying at room temperature by crystallization, thereby maintaining the cresylate in Working condition.

p 4. The process of claim 3, and further, neutralizing the mixture of cresylate and Water to a pH of at least 6.2 by adding a mineral acid to free the primary tar acids from the solution of. aqueous alkali metal hydroxide.

'5. The process of claim 3, and further, neutralizing the mixture of water and cresylate by a mineral acid to free the primary tar acids from the solution of aqueous alkali metal hydroxide.

6. The process of claim 5, and further, subjecting the freed primary tar acids from the solution of cresylate in aqueous alkali metal hydroxide to fractional distillation to obtain individually the primary tar acid members.

7. The process of producing purified primary tar acids from a solution of cresylate in aqueous alkali metal hydroxide containing primary tar acids, unsattuates and other contaminating hydrocarbons, said tar acids having been formed from low temperature distillation of a member selected from the group consisting of oil shales, bituminous coal, sub-bituminous coal, lignite coal, and mixtures thereof, comprising simultaneously subjecting 9 10 said solution of cresylate in aqueous alkali metal hydrox- References Cited in the file of this patent ide to pro ressively increasing elevated temperatures and increased alkali metal hydroxide concentration caused by UNITED STATES PATENTS dehydration vapors formed by heat of a temperature mag- 1,945,376 Peake J an. 30, 1934 nitude of the order of 120 C.160 C. at atmospheric 5 2,040,101 Miller May 12, 1936 pressure, said vapors carryin off the freed unsaturated and other contaminating hydrocarbons leaving the pri- FOREIGN PATENTS mary tar acids undistilled as purified cresyla te. 678,192 Great Britain Aug. 27, 1952 

1. THE PROCESS OF PRODUCING PRIMARY TAR ACIDS FROM CRUDE COAL TAR AND SHALE OILS OBTAINED BY LOW TEMPERATURE DISTILLATION OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF OIL SHALE, BITUMINOUS COAL, SUB-BITUMINOUS COAL, LIGNITE COAL, AND MIXTURES THEREOF, SAID SHALE OILS AND SAID CRUDE COAL TARS COMPRISING LIGHT TAR OIL FRACTION AND HEAVY TAR OIL, COAL TAR PITCH AND CREOSOTE, SAID LIGHT TAR OIL FRACTION COMPRISING THE INTERMIXTURE OF PRIMARY TAR ACIDS, NEUTRAL OILS AND UNSATURATED AND OTHER CONTAMINATING HYDROCARBONS FROM WHICH INTERMIXTURE THE PRIMARY TAR ACIDS ARE TO BE SEPARATED, SAID PROCESS COMPRISING THE FOLLOWING STEPS IN SEQUENCE: SEPARATING THE LIGHT TAR OIL FRACTION; REACTING THE LIGHT TAR OIL FRACTION WITH AN ALKALI METAL HYDROXIDE IN AQUEOUS SOLUTION THE CONCENTRATION OF WHICH IS EFFECTIVE TO FORM A SOLUTION OF CRESYLATE IN AQUEOUS ALKALI METAL HYDROXIDE AND FREEING SUBSTANTIALLY THE NEUTRAL OIL PART OF SAID FRACTION; SEPARATING SAID NEUTRAL OIL PART BY VIRTUE OF ITS SPECIFIC GRAVITY FROM THE SOLUTION OF CRESYLATE IN AQUEOUS ALKALI METAL HYDROXIDE WHICH SOLUTION OF CRESYLATE IN AQUEOUS ALKALI METAL HYDROXIDE THEN COMPRISES THE PRIMARY TAR ACIDS, UNSATURATED AND OTHER CONTAMINATING HYDROCARBONS; AND SEPARATING SAID PRIMARY TAR ACIDS FROM THE UNSATURATED AND OTHER CONTAMINATING HYDROCARBONS BY SIMULTANEOUSLY SUBJECTING SAID SOLUTION OF CRESYLATE IN AQUEOUS ALKALI METAL HYDROXIDE TO PROGRESSIVELY INCREASING ELEVATED TEMPERATURES AND INCREASED ALKALI METAL HYDROXIDE CONCENTRATION CAUSED BY DEHYDRATION VAPORS FORMED BY HEAT OF A TEMPERATURE MAGNITUDE OF THE ORDER OF 120*C.-160*C. AT ATMOSPHERIC PRESSURE, SAID VAPORS CARRYING OFF THE FREED UNSATURATED AND OTHER CONTAMINATING HYDROCARBONS LEAVING THE PRIMARY TAR ACIDS UNDISTILLED A PURIFIED CRESYLATE. 